THIS invention relates to a method of forming a composite structure from a support structure or a plurality of support structures on a base, and to an article for use in forming such a support structure.
It is well known to form composite or support structures such as roadways, canal or river or bank linings, mine packs, sea walls or the like, from a material having a honeycomb structure, i.e having a plurality of compartments or cells divided by dividing walls, each compartment or cell being filled with a suitable filler material. Examples of such materials for use in the support structures are Hyson-Cells from M and S Technical Consultants and Services (Pty) Limited, Geoweb from Presto Products Co, Tenweb from Tenax Corp, Armater from Crow Company, Terracell from Webtec Inc, Envirogrid from Akzo Nobel Geosynthetics Co and Geocells from Kaytech.
All these materials have a common feature that the size of the compartments or cells in the material is the same. In other words, in any sheet of the material, all the cells or compartments in that sheet have the same size. There are however applications where it would be useful to have a material of this type with compartments of different sizes.
According to a first aspect of the invention there is provided a method of making a composite structure from a support structure or a plurality of support structures laid side-by-side, on a base, each support structure being formed from a framework comprising a tube of a flexible material divided by dividing walls of a flexible material into an array of compartments or cells running the length of the tube, the compartments being arranged in rows and columns so that the tube divided by dividing walls has a honeycomb structure, which method includes the steps of:
(a) locating a framework or a plurality of frameworks side-by-side, on the base;
(b) filling some or all of the compartments with a filler material;
which is characterised in that either at least one framework includes compartments with two different sizes or in that at least two adjacent frameworks have compartments of different sizes, the size of a compartment being the cross-sectional area thereof at right angles to the axis of the compartment.
In one embodiment of the invention, a composite structure is formed from a single support structure or from a plurality of support structures, wherein each support structure is formed from a framework which includes compartments with two different sizes.
In this case, each framework preferably includes one or more rows of compartments with a first size and one or more rows of compartments with a second size.
There may also be a row of compartments with a transitional size between the last row of compartments with the first size and the first row of compartments with the second size.
Preferably, the compartments with the second size are a quarter of the size of the compartments with the first size.
Each framework may also include one or more rows of compartments with a third size, the compartments with the third size being a quarter of the size of the compartments with the second size, and so on, with each succeeding set of compartments with a lesser size being one quarter of the size of the preceding compartments.
In a further embodiment of the first aspect of the invention, the composite structure may be formed from a plurality of support structures, each support structure being formed from a framework, wherein at least two adjacent frameworks have compartments of different sizes. In other words, a first framework will have compartments of a first size and an adjacent framework will have compartments of a second size.
Preferably, the compartments of one framework are a quarter of the size of the compartments of the adjacent framework.
In this case, every second smaller compartment may be joined to a respective larger compartment, every other smaller compartment being joined by a brace to the adjacent framework at a point where two larger compartments are joined.
The framework, i.e the tube and the dividing walls, may be made from any suitable flexible material. Although the material must possess some degree of flexibility, the degree of flexibility may range from very flexible up to semi-rigid. The flexible material may be for example a plastics material such as for example a co-extruded or a biaxially extruded plastics material; a plastics laminate material such as for example a laminate of a plastics material and a metallic material or a textile material; a metallic material; a woven or non-woven textile material; a paper or cardboard material; and the like. The flexible material is preferably a suitable plastics material.
The framework may include a plurality of holes therethrough to permit drainage of any liquid substance through the holes and from the framework.
The framework may have any suitable height and any suitable compartment size, provided of course that in any support structure or composite structure formed, there is included compartments of at least two sizes. For example, the height of the framework may range from 2 mm to 10 m inclusive, and each compartment may have a wall length of from 5 mm up to 2 m.
In addition, within a particular framework or in adjacent frameworks, the heights of the compartment walls may vary, so that a first compartment adjacent a second compartment may extend beyond the second compartment, either at the top or at the bottom.
The compartments in the framework may have any suitable cross-section, such as square, hexagonal or octagonal, but preferably have a square cross-section, i.e each compartment is defined by four walls of substantially equal lengths.
The filler material may be any suitable filler material, depending on the nature of the composite structure to be formed. For example, when the composite structure to be formed is a roadway or a paved area, a lining for a canal, river, drain or spillway or the like, a support for an embankment, or a dam or harbour wall, then the filler material may be an inert filler material, .e.g sand or gravel or the like, or a composition comprising a filler material and a settable binder therefor. Examples of such compositions include:
(i) an inert filler material such as sand or gravel or the like, and a cementitious binder, for example ordinary Portland Cement;
(ii) an inert filler material such as sand or gravel or the like and a bituminous binder;
(iii) a filler material such as soil treated with a suitable chemical composition such as calcium chloride, a lignin sulphonate or an ionic liquid to cause the soil to bind or set;
(iv) a filler material such as sand or gravel or the like and a resin binder, for example (a) a thermosetting resin such as polyurethanes and polyesters, (b) a thermoplastic resin such as polyethylene, EVA, or PVC, and (c) a suitable wax.
The settable composition may include a conventional foam or foaming agent so that the final set composition is a foamed composition, to reduce the weight thereof.
Alternatively, when the composite structure is a purification pack or the like, for example for the purification of liquids such as water, or gasses, then the filler material may be any material suitable for purification, e.g diatomaceous earth, an ion exchange resin or the like.
In the method of the invention, the framework or frameworks may be supported in position by the use of flexible strings or rigid stays as is disclosed in a co-pending patent application. In addition, the wall or walls of each compartment in a framework may include one or more hollow protrusions or one or more hollow recesses so that the compartments protrude into or are protruded into by adjacent compartments to interlock adjacent compartments, as is disclosed in a further co-pending patent application.
According to a second aspect of the invention there is provided a framework comprising a tube of a flexible material divided by dividing walls of a flexible material into an array of compartments or cells running the length of the tube, the compartments being arranged in rows and columns so that the tube divided by dividing walls has a honeycomb structure, wherein the framework includes compartments with two different sizes, the size of a compartment being the cross-sectional area thereof at right angles to the axis of the compartment, the framework being for use in making a support structure on a base.